Field of the Invention
Embodiments of the present invention relate to connecting gas turbine engine annular members and, particularly, to such members having different thermal expansion coefficients and used in hot sections of the engine.
Description of Related Art
Many annular members of gas turbine engines are generally made of metal and held together by axially extending bolts through bolt holes provided in flanges of the annular members. Examples of such members include centerbodies and mixers located downstream of turbines of the engine and which are used to mix fan bypass airflow with core engine airflow exiting the turbines. Centerbodies and mixers are typically mounted to a metallic rear turbine frame of the engine. Other examples of such members include ducts, cowls, combustor liners, and shrouds.
These annular members in a gas turbine engine hot section are subject to very high temperatures and it has been suggested to make some of them from high temperature composite materials such as ceramic matrix composite (CMC) material. The CMC or composite annular members are mounted to and supported by metallic annular members. Unfortunately, metal materials and composite materials have coefficients of thermal expansion that are very different. This gives rise to particularly severe problems in making connections between the CMC or composite annular members and the supporting metallic annular members at the interface of the two types annular members. The problem is further compounded by the brittleness of CMC.
Thus, it is highly desirable to provide a connection to connect and support a first annular member from a second annular member in a hot section of a gas turbine engine wherein the first and second annular members are made of materials have very different coefficients of thermal expansion. It is highly desirable to provide such a connection wherein the first annular member is made from high temperature composite materials such as ceramic matrix composite (CMC) material and the second annular member is metallic. It is also highly desirable to provide such a connection wherein the first annular member is a CMC centerbody or mixer attached to and supported by a metallic annular rear turbine frame of the engine